Messages in this thread | | | Date | Tue, 12 Jul 2011 11:59:07 -0700 | From | "Paul E. McKenney" <> | Subject | Re: PROBLEM: 3.0-rc kernels unbootable since -rc3 |
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On Tue, Jul 12, 2011 at 02:01:51PM -0400, Konrad Rzeszutek Wilk wrote: > > > http://darnok.org/xen/loop_cnt.log > > > > > > which seems to imply that we are indeed stuck in that loop > > > forever. > > > > It does indeed, thank you! Also it looks like interrupts are > > disabled, and that timekeeping is similarly out of action. > > .. With the latest patch the time looks to be advancing.
Sounds like an improvement. ;-)
> > Disabling CONFIG_NO_HZ would be an interesting test case. > > Hadn't done that yet. Compiling a kernel with "# CONFIG_NO_HZ is not set" > right now. > > > > > > o Problems due to portions of the code attempting to use > > > > RCU read-side critical sections while in dyntick-idle mode. > > > > Frederic Weisbecker has located some of these, (though not yet > > > > in Xen) and he has some diagnositics which may be found at: > > > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu.git > > > > > > > > on branch eqscheck.2011.07.08a. > > > > > > > > You need to enable CONFIG_PROVE_RCU for these diagnostics to > > > > be executed. > > > > > > Ok, let me try those too. > > > > Thank you! > > Will shortly do this. > > > > > > o As always, there might be bugs in RCU. ;-) > > > > > > > > But the loop in task_waking_fair() looks like the most prominent smoking > > > > gun at the moment. > > > > And could you also please try out the patch that I posted earlier? > > With the previous patch and the .. this is getting confusing. With this patch: > http://darnok.org/xen/loop_cnt-extra.patch
That is indeed the patch I intended.
> I get this output: http://darnok.org/xen/log.loop_cnt-extra-patch (one guest > with 4 VCPUS) and http://darnok.org/xen/loop_cnt-extra-patch.log (the guest with 16 VCPUs)
OK, so the infinite loop in task_waking_fair() happens even if RCU callbacks are deferred until after the scheduler is fully initialized. Sounds like one for the scheduler guys. ;-)
Thanx, Paul
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